How to deal with a negative coworker?

Dealing with negativity is never an easy thing.
Try to hear the person out and see if there is some basis for the negativity from a neutral platform (although it is next to impossible, try not to let it affect you).
Some people are chronic whiners/pessimists - the best thing is to ignore them gracefully and continue doing your work.
If they start interfering within your space then it is important to have a conversation with the person and expectations should be set clearly.
There are those who are negative because they are insecure with your performance and do not want you to progress and neither themselves - it is best to completely ignore these people and let them know you are ignorning them and that their attitude will not affect you - sooner or later they will fall in line.
If they try to impede your progress, you should document it and bring it to the attention of your HR representative.

Tips for Dealing With Occasional Negativity Listen to the employee or coworker’s complaints until you are certain that they feel heard out and listened to.
Decide if you believe the employee or coworker has legitimate reasons for their negativity.
If you decide affirmatively, ask if they’d like your help to solve the problem.
If they ask for help, provide advice or ideas for how the coworker can address the reason for their negativity.
Short term advice that points a person in a positive direction is welcome.
But, your role is not to provide therapy or counseling.
Nor, is your role to provide comprehensive career advice or long term recommendations.
Point the coworker to helpful books, seminars, or the Human Resources Department to solve their problem.
Know your limits when advising coworkers.
Sometimes, the coworker just wants to complain to a friendly, listening ear; they don’t want your advice or assistance to address the situation.
Listen, but set limits so the coworker does not overstay or over-talk his or her welcome.
Long term complaining saps your energy and positive outlook.
Don’t allow that to happen.
Walk away.
Tell the coworker you’d prefer to move on to more positive subjects.
If you listen to the coworker’s negativity, and decide the concerns are not legitimate, practice personal courage and tell them what you think.
Tell the coworker you care about their concern and about their happiness at work, but you disagree with their assessment of the situation.
Back gracefully out of additional conversations.
The coworker will attempt to appeal to your sympathetic nature, but if you believe the negativity is unwarranted, don’t spend your time listening or helping the coworker to address the negative feelings.
You will only encourage long term and growing negative feelings and, potentially, behavior.
You will set yourself up as a negativity magnet.
Constant negative interactions will eventually permeate your interaction with your workplace.

Dealing with a negative coworker is something that every professional faces at some point during their career.
We've already got some great answers addressing this issue.
Negative people tend to wallow in negativity and drain you of your optimism as well.
There’s always a trend, i.e.
complaints about work, the job, the manager, the company in general, and almost everything else.
If you would like to help this coworker, try and understand the reason for his/her negativity.
Listen objectively so that you don’t get dragged into the ‘negativity ditch’ as well.
Address the complaints of your coworker, again objectively and help them see light at the end of the tunnel.
Once you have addressed the concerns of your coworker, try and focus on the positive.
This might be an exercise you might have to conduct more than once or twice.
When you start noticing a positive difference, it would make an impact if you actually do something positive for this coworker and/or publicly acknowledge this person.
Positive actions almost always have a positive impact as well.

These are my thoughts on this topic: To begin with, one must define what is Negative about this co-worker - i.e if the Negativity is related to one's Work Place or One's Attitude about Life (Personal or In General).
If the negativity is generally about Life, this co-worker may have gone through a tough or bad phase and just needs someone to give him/her a more positive and hopeful outlook about life.
Counseling - A Listening Ear, mentoring, personality training can help such a co-worker.
If the negativity is specific to one's Work Place, then either the Co-worker has some unresolved issues that have not been addressed or have been overlooked.
His/her outlook may steer towards the concern that no one listens or that some Negative Aspects in the Organization just don't seem to change.
There may be situations where the Co-worker's colleagues are driving him/her towards a Negative Outlook.
In such a case, it is best to understand the Co-worker's side of the story and resolve his/her issues within reasonable means.
Try to change the Co-workers scenario - Give him/her a new or more responsibility, new office colleagues/team and an opportunity to change positively.

Negativity in the workplace is contagious.
Therefore, it is important that you know how to handle negative co-workers.
Being negative is a result of dissatisfaction in work or personal life.
These people needs someone who can sympathize with them.
They need people who can listen as they air their sentiments.
You can be of great help to these colleagues by hearing them out.
But avoid giving bad comments because most them get easily offended.
Also most negative thinkers are cynics, so sheding a little light of hope would also be great.

Ok, I'll be short and to the point.
First of all try to find out the reasoon of the negativity either by a short and meaningful talk with the co-worker or by observing closely.
decide wether the reason is legitimate or not.
Once you find out the reason then you are ready for the remedy:1) If the reason is legitimate try to help him out by recommending proper solution, or if it is something you said or did appologise.2) If the reason is not legitimate ignore his negativity and reply it with positivity.
Always try to do good for him and never try " Tit for tat".
As a Muslim also we are taught to do the same.

First try to understand him/her and know the reason and circumstances behind it, then take appropriate steps according to that.

To speak with him positively and objectively in order to understand right and try him in more than one way to succeed in understanding him, and if it had not been any attempts with successful managers told to act with him

No matter if any your coworker is negative thinking owner, just listen him and wait that what can he do,,, he will come beck when he destroyed, and will share own thinking with you...

Ignore him.
Don't let your co-worker's negativity suck you in.
Refuse to banter back and forth with him unless the conversation is positive.
After a while, he will get the hint.
Speak "up".
Let your words be seasoned with love, hope and joy.
You're negative co-worker may not understand your speak-style, but eventually he will appreciate it.
Be honest.
Deal with your negative co-worker by telling him how you truly feel.
His behavior is bringing you down.
You don't want to work in this way and would like him to change.
Offer help.
If your co-worker isn't normally negative and has changed because he's upset, offer help.
Take on more work or discuss counseling options.
Help your co-worker deal with the problem so he can get back to his usual happy self.
Switch desks.
Ask your boss to move you.
You can state the real reason or use an alternative one.
Either way, do what's best for you.
Don't let a negative co-worker ruin your career or day.
Change topics.
Don't indulge in a drawn out low brow conversation with your negative co-worker even if it's true.
Cut them off halfway through the conversation and change topics.
Talk about something that is positive or neutral.
Set expectations.
Sometimes the best way to deal with a negative co-worker is to set expectations.
Announce that you plan on having an upbeat day full of positive sayings.
This works well with a person who is new to the job.

To handle the issue:1.
We should not ignore the it, otherwise it will escalate.
sometimes difficult employees don't know that their behavior is an issue, while others consider it as a normal job frustration.
so it 's the direct manager responsibility to address the issue to the employee and give his feed back to him or get the hr involved for their advice and support before addressing the issue.2.
It is important to get the employee feedback to check if he is aware of the negative attitude and specifying the unwanted behavior by evidence and coach him/her on how to overcome this default and introduce the proper behaviors and giving him time to practice it.3.
HR and direct manager has to review it by the end of the agreed period and encourage the employee if they found a positive change even it is slight or happening slowly.
if the issue continues, in some cases the termination might be necessary, specially if the employee insists to deny that negative attitude and that is affecting the whole department or the business.
keeping a documented feedback is vital in that regard.